Lessons learned from linking two complementary databases: the Society of Thoracic Surgeons Congenital Heart Surgery Database and The Vermont Oxford Network Expanded Database.

The Society of Thoracic Surgeons Congenital Heart Surgery Database and the Vermont Oxford Network Expanded Database are both large, international, well-established quality and outcomes databases with high penetration in their respective fields of congenital heart surgery and neonatology. Previous studies have shown the value of combining large databases for research purposes. Our aim was to examine the feasibility and value of combining these databases on a local level.We included patients from both databases, cared for at our centre and born from 2015-2020, who had cardiac surgery as neonates or during the birth hospitalisation. We examined the number of patients from each database and overlap between the two. We compared cardiac diagnoses, surgeries performed, pre-operative factors, mortality, and length of stay between databases.Of the 255 patients meeting criteria, 209 (81.9%) had records in both databases. The most common diagnoses in both were hypoplastic left heart syndrome, coarctation, and transposition of the great arteries. Surgical data were incompletely recorded in Vermont Oxford. Gestational age, birth weight, multiple gestation, mortality, and length of stay did not differ significantly between the databases, while the percentage of patients with an extracardiac malformation or genetic syndrome recorded was higher in the Society for Thoracic Surgeons group.Larger-scale matching and comparison studies using these databases are feasible and desirable; for some variables, a record with data from both databases may be more complete. Specific attention should be given to inclusion criteria, reconciling different schema of diagnoses, and formulating questions relying on each database's relative strengths.